Personalized T-Rex Dinosaur 5th Birthday Youth Long Sleeve T-Shirt. A grumpy, purple T-Rex wearing a birthday hat sits and eats a birthday cupcake. Cute 5th birthday gift for your little five year old. youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)